You know sunrise sunset from weewx so it’s possible to tweak the code accordingly too… On Friday, June 26, 2026 at 1:53:00 PM UTC-7 David Hathaway wrote:
> Very cool to see it in python! I only note that the AI agent added a > daylight adjustment: > > *Step 3: Daylight Adjustment for WBGT* > - Daylight is defined locally as approximately 6:30 AM – 8:15 PM in summer > for Sugar Land, TX. > - Because it is daytime and the sun is contributing radiant heat, the > following adjustment is applied: > > WBGT ≈ Tw + ((T − Tw) × 0.35) + 3.5 > > This accounts for the additional heat load from direct sunlight. > > *Result:* WBGT = 92.3 °F > > That added 7 degrees, which ain't nothing. Not sure if it is valid, but > it gets it closer to how I feel outside. 95F at mid day here in the Gulf > Coast doesn't feel like a comfy 85F, it feels way hotter. > > The other suggestion is to add the warning text. The whole reason I > started looking at WBGT was because my sports trainer friend said that > based on those categories, sports teams are mandated different things. > Like maybe a cooler with ice and a tarp, so that if a player falls out > because it is Extreme they are wrapped in an ice cocoon. > > Dave > > On Friday, June 26, 2026 at 11:44:29 AM UTC-5 [email protected] wrote: > >> I added this to the new-belchertown skin. >> Straightforward. >> Add user.wetbulb.WetBulbService to data_services line >> Add wetbulb.py to your weewx-data/bin/user directory >> Drop index_hook_after_charts.inc into /skins/new-belchertown >> Restart weewx and then weectl reports run >> >> Look at the bottom of the page and you should see the status >> >> >> >> >> On Tuesday, June 23, 2026 at 3:35:59 PM UTC-4 David Hathaway wrote: >> >>> Very interesting! I have been asking an AI agent to estimate the WBGT >>> for me, and now I asked it what it was using. It uses the Stull formula >>> and then a crude radiant heat adjustment. I think it is close enough for >>> me to caution my wife to come in frequently so she doesn't perish. I'm >>> frequently surprised that the WBGT is lower than our actual temperature and >>> far below the "feel's like" that we are accustomed to. >>> >>> The agent says: >>> >>> *WBGT Calculation – Full Explanation* >>> >>> The process follows the weather-wbgt-safety skill, which uses local >>> WeeWX data and standard approximations suitable for practical heat-stress >>> assessment. >>> >>> *Step 1: Data Source* >>> - The local RSS file at /www/rss.xml is read directly. >>> - Current values extracted: >>> – Outside Temperature (*T*): 95.4 °F >>> – Outside Humidity (*RH*): 65 % >>> – Wind: calm (not used in the WBGT formula here) >>> – Timestamp: 13:40 CDT (used to determine daylight) >>> >>> *Step 2: Wet-Bulb Temperature (Tw)* >>> Wet-bulb temperature is calculated using *Stull’s approximation* (a >>> reliable, widely used empirical formula that avoids needing a full >>> psychrometric chart). >>> >>> 1. Convert *T* from °F to °C. >>> 2. Apply Stull’s formula (all temperatures in °C, RH in %): >>> >>> Tw = T × atan(0.151977 × √(RH + 8.313659)) + atan(T + RH) − atan(RH − >>> 1.676331) + 0.00391838 × (RH¹·⁵) × atan(0.023101 × RH) − 4.686035 >>> >>> 3. Convert the resulting *Tw* back to °F. >>> >>> *Result:* Wet-bulb temperature = 85.3 °F >>> >>> *Step 3: Daylight Adjustment for WBGT* >>> - Daylight is defined locally as approximately 6:30 AM – 8:15 PM in >>> summer for Sugar Land, TX. >>> - Because it is daytime and the sun is contributing radiant heat, the >>> following adjustment is applied: >>> >>> WBGT ≈ Tw + ((T − Tw) × 0.35) + 3.5 >>> >>> This accounts for the additional heat load from direct sunlight. >>> >>> *Result:* WBGT = 92.3 °F >>> >>> *Step 4: Risk Classification* >>> The value is compared against standard thresholds (in °F): >>> >>> - < 80 → Low >>> - 80–85 → Moderate >>> - 85–88 → High >>> - 88–90 → Very High >>> - > 90 → Extreme >>> >>> At 92.3 °F the conditions fall into the *Extreme* category, triggering >>> the safety guidance. >>> >>> This method gives a practical, conservative estimate without requiring >>> specialized instruments (black-globe thermometer, etc.). It is intended for >>> personal decision-making rather than official occupational safety >>> compliance. >>> On Tuesday, June 23, 2026 at 2:19:25 PM UTC-5 Rainer Lang wrote: >>> >>>> the story is rather simple - it refers to how WGBT is determined and >>>> what is supported by them. >>>> The general formula for determining WBGT outdoors is: >>>> WGBT = 0.7 x Tnwb + 0.2 x Tg + 0.1 x Ta >>>> where nbw is natural wet bulb, g is BGT and a is outdoor temperature >>>> - to get Ta in an Ecowitt context, you need an outdoor T&H sensor >>>> (e.g. WH32) >>>> - to get Tg in an Ecowitt context, you need a WN38 Black Globe >>>> Temperature sensor >>>> - to get Tnwb there is no sensor provided - therefore an approximation >>>> method is being used >>>> only in this combination Ecowitt provides WBGT data >>>> and as WBGT has a medical dimension, the disclaimer is on there in >>>> their (Ecowitt) web shop >>>> >>>> there are basically two approximation methods for determining Tnwb and >>>> Tg >>>> 1. the so-called Stull formula which uses temperature, humidity and air >>>> pressure (and derived entities like water saturation pressure) >>>> 2. the so-called Lijlegren approximation which also uses wind speed >>>> and, depending on the accuracy targeted, also sometimes solar radiation >>>> values (direct, indirect, at different wave-lengths ...) >>>> >>>> 1. the Stull approximation implemented in the firmware now (and used by >>>> many others) can lead to a deviation of up to 3° C >>>> 2. is quite a sophisticated approach with several iterations, depending >>>> on if the approach is used for Tnwb only or for Tnwb + Tg and if >>>> solar values are included or not >>>> >>>> >>>> to program the full Lijegren approach to reach a < 0.1% deviation from >>>> a nbw-sensor, a coding of 300 - 400 lines of code is needed due to >>>> repetetive iterations (so 'they' say) >>>> - for so-called "medical" (health related) purposes, a simplified >>>> Lijlegren approach can be used also using wind speed and it produces a >>>> deviation of < 0.3° C - that's sufficient for the WGBT tiers/windows used >>>> in different areas >>>> - Ecowitt is considering to replace the Stull formula used now by a >>>> simplified Llijlegren approach including wind speed to reach a higher >>>> degree of accuracy >>>> so, the accuracy of WBGT values provided by any piece of weather >>>> station firmware or data logging software (like weewx) will depend on the >>>> approach used. >>>> >>>> >>>> On 23.06.2026 20:38, David Hathaway wrote: >>>> >>>> Thanks for the discussion pointer. I'll go snoop. >>>> >>>> On Tuesday, June 23, 2026 at 1:09:37 PM UTC-5 Vince Skahan wrote: >>>> >>>>> I recently saw mention of https://shop.ecowitt.com/products/wn38 >>>>> which has a disclaimer that I didn't look into further. >>>>> >>>>> *"The WN38 Black Globe Thermometer measures and displays the black >>>>> globe temperature only, which can be viewed on the LCD screen or through >>>>> the Ecowitt or WS View Plus app.* >>>>> >>>>> *To display WBGT (Wet Bulb Globe Temperature) data in the app, the >>>>> WN38 must be used together with an Ecowitt outdoor temperature and >>>>> humidity >>>>> sensor from either an outdoor array or a WN32(WN31 is not feasible)."* >>>>> >>>>> There is a lot of discussion at >>>>> https://www.wxforum.net/index.php?topic=49316.0 which might be worth >>>>> a read. Hope this helps. >>>>> On Wednesday, June 10, 2026 at 10:03:28 AM UTC-7 David Hathaway wrote: >>>>> >>>>>> There is a 'wetbulp.py' (note the p) in this group that calculates it >>>>>> as a xtype_service. This conversation, >>>>>> >>>>>> https://groups.google.com/g/weewx-user/c/FntQukhWY00/m/lM53yFt7AwAJ >>>>>> >>>>>> >>>>>> On Wednesday, June 10, 2026 at 11:48:33 AM UTC-5 Vince Skahan wrote: >>>>>> >>>>>>> Quick search seems to say a WeatherFlow Tempest station has this, >>>>>>> but I can't find it mentioned in any of their API so I don't see a way >>>>>>> to >>>>>>> get it into weewx for this one model station - >>>>>>> https://community.tempest.earth/t/wet-bulb-globe-temperature/14386/11 >>>>>>> >>>>>>> Other threads and docs with the formula seem to say you need special >>>>>>> sensors for this, so I can't speculate how WeatherFlow fakes something >>>>>>> to >>>>>>> generate that item. >>>>>>> >>>>>>> On Wednesday, June 10, 2026 at 8:36:45 AM UTC-7 David Hathaway wrote: >>>>>>> >>>>>>>> As the FIFA World Cup (tm) ramps up, we here in Houston are getting >>>>>>>> a load of notices about how there is a mandatory water break in >>>>>>>> matches, >>>>>>>> even though it is played indoors. :-/ As I discussed this with my >>>>>>>> friend >>>>>>>> the sports trainer, he mentioned that Texas now has a rule that they >>>>>>>> must >>>>>>>> do certain things according to the WBGT. >>>>>>>> >>>>>>>> I have searched here for wet bulb additions to WeeWx. I see >>>>>>>> discussions from 2024 and wonder if there is someone with a more >>>>>>>> recent >>>>>>>> idea about implementing this. Does anyone calculate the Risk Level >>>>>>>> and >>>>>>>> provide Guidance? >>>>>>>> >>>>>>>> I am trying out an agentic Ai to read the RSS XML feed; It loves >>>>>>>> this format. I've not messed with the RSS export. Is there some >>>>>>>> intrisic >>>>>>>> gotcha? I really only care about current values. >>>>>>>> >>>>>>>> Dave >>>>>>>> >>>>>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "weewx-user" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion visit >>>> https://groups.google.com/d/msgid/weewx-user/29861e34-51f9-4df4-86e0-c9e06cdbdda0n%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/weewx-user/29861e34-51f9-4df4-86e0-c9e06cdbdda0n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/weewx-user/c8964637-0863-4522-baec-96d2cdc0effbn%40googlegroups.com.
